Concrete products are produced by kneading materials such as cements, aggregates, water and dispersants (water reducing agents), placing in forms, and aging (curing). From the viewpoint of productivity (increasing a turnover rate of a form), it is important that a concrete product exhibits high strength in its initial stage. To achieve this, some measures have been taken, including (1) using an early-strength cement, (2) using various polycarboxylic acid compounds as an admixture to decrease a water amount in a cement composition, and (3) employing steam aging as a method of aging. From demands for higher productivity at this time, more shortened processes for aging may be requested. For example, some concrete products are required to exhibit a high strength (initial strength) after 16 hours aging. In general, an aging process includes complicated steps including a step of heating with steam and the like. Countermeasures for increasing an initial strength by changing a system design of these processes are not good practical means. Therefore, from the points of production cost and the like, there is a strong demand of the market for a simple method of producing a concrete having a high initial strength without changing a system design.
In addition, to shorten an aging period, steam aging is generally employed. However, use of steam leads an increased energy cost. Also from the viewpoint of reduction in energy cost (shortened period of steam aging/decreased aging temperature), there is a strong demand for such a method.
JP-A 2006-282414 discloses a strength improving agent for cement containing glycerol or an alkyleneoxide adduct to glycerol and a specific polycarboxylic acid copolymer.
JP-A 9-194244 discloses that a cement admixture is a combination of a compound selected from a polyether compound, being a dihydric alcohol, a sulfated compound thereof and a salt thereof with a sulfonic group-containing copolymer and the admixture is excellent in fluidity, slump-retaining property and air-retaining property,
JP-A 7-10624 discloses an additive to cement, containing a sulfated polysaccharide, having a water-reducing property, a moderate viscosity and solubility in water, but not an excessive air-entraining property and an excessive curing-retarding property.
JP-A 9-194244 and JP-A 7-10624 do not suggest that sulfation of a polyhydric alcohol as a raw material shortens a curing time (causing faster curing) or increases an initial age strength (strength in short time) at room temperature after aging of, for example, 16 hours.
Further, in JP-A 9-194244, no remarkable difference in effects of fluidity, slump-retaining property and air-retaining property is observed between a polyether compound and a sulfated compound thereof.